JPS5892592A - Single substance pressure sensitive recording sheet - Google Patents

Abstract

PURPOSE:To obtain the titled single substance pressure sensitive recording sheet for copying paper and the like, wherein a specified amount of pulp powder, whose weight averaged fiber length is limited is included in a homogeneously mixed liquid of microcapsules including a color former and a coloration agent, coloring stain is avoided, and recording and printing compatibility is improved. CONSTITUTION:The simple substance pressure sensitive recording sheet wherein the pulp powder, whose weight averaged fiber length (TAPPI standard T232, SU-68) is 20-80mu, is included in the homogeneously mixed liquid of the microcapsules including the color former and the coloration agent (e.g. activated clay and the like). The ratio is 40-200pts. of the pulp powder with respect to 100pts. of the microcapsules (weight; converted into the solid state component). The sheet is formed by applying said homogeneously mixed liquid including said pulp powder to a supporting body (paper, sythetic film, and the like).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a single pressure-sensitive recording sheet that improves color development stains caused by contact, rubbing, etc. without reducing color development properties, and also improves printability.

A single pressure-sensitive recording sheet is a type of pressure-sensitive copying paper that utilizes a color reaction between an electron-donating color former and an electron-accepting color former, and consists of microcapsules containing oil droplets in which a color former is dissolved and a color former. It is constructed by laminating the entire support (usually microcapsules are the lower layer and the coloring agent is the upper layer) or by coating them in a single layer by mixing them.

Such a single pressure-sensitive recording sheet, like ordinary pressure-sensitive copying paper, has the disadvantage that the microcapsules are destroyed by external pressure such as slight contact or rubbing, resulting in colored stains.

In order to improve these drawbacks, ordinary pressure-sensitive copying paper generally contains particulate matter (for example, cellulose powder, starch granules, or polyolefin fine particles) that is thicker than the particle size of the microcapsules in the coating layer of the microcapsules. A method has been adopted in which capsules are dispersed (powder, etc.) as a stilt material (buffering agent) and supported by a stilt material that protrudes against contact and abrasion to reduce capsule breakage. However, even with stilt materials, there is a problem in that the amount of starch granules and polyolefin thread fine powder added is closely related to the color development, and as the amount added is increased, the color development decreases. On the other hand, in the case of cellulose powder, the relationship between the amount added and color development is not the same as that of starch granules or fine polyolefin thread powder. For this reason, powdered powder has been widely used as a stilt material since ancient times. The amount used is usually about 20 to 30 parts by weight per 100 parts by weight of microcapsules. Incidentally, if it is used for any longer than this, the fluidity of the coating solution will be extremely deteriorated, which will not only reduce its suitability for coating onto the support, but also roughen the coated surface, impairing its suitability for printing, and further reducing its suitability for copying. It will be Rikoto.

The need to prevent colored stains due to contact and abrasion is the same for single pressure-sensitive recording sheets, but due to their structure, colored stains are more likely to occur than with ordinary pressure-sensitive copying paper.
Furthermore, even among individual pressure-sensitive recording sheets, single-layered recording sheets are more likely to become dirty than laminated-layered ones.

However, from the viewpoint of production, it is advantageous to make single-layer pressure-sensitive recording sheets because only one coating step is required, and from the viewpoint of color development, it is advantageous to make single-layer sheets, and from the viewpoint of color development, it is advantageous to make single-layer sheets. This has the advantage that good recording can be obtained even with low pressure because the coloring agent and the coloring agent are mixed and close together.
Ideally, it would be possible to produce a single-layered product with little colored staining. However, most of the products that have actually been commercialized are in the laminated form, and there are only a few in the single layer form.

The ones on the market are also colored and dirty, have minimal recording suitability, and are still quite unsatisfactory in terms of quality. The current situation is that this has not been achieved.

Therefore, the present inventors have conducted various studies, particularly in the field of stilt agents, in order to develop a single-layer pressure-sensitive recording sheet with less colored stains and excellent recording and printing suitability. It was completed. That is, the present invention
In a single pressure-sensitive recording sheet made by coating a support with a uniform mixture of color-forming agent-containing microcapsules and a color-forming agent and drying it,
The homogeneous mixed liquid contains 40 to 200 parts by weight of pulp powder having a weight average fiber length (TAPPI Standard T282, 8U-68) of 20 to 80 μ per 100 parts by weight of microcapsules (in terms of solid content). It is something to do.

In the above structure, the pulp powder used must have a weight average fiber length of 20 to 80μ, because if a fiber length of 80μ or more is used, the coated surface will become rough and printability will deteriorate. In addition, if it is less than 20μ, the effect of preventing colored stains is low.Incidentally, the papule powder used in conventional pressure-sensitive copying paper is particularly effective in preventing colored stains. Papers with a high Nutilt effect, that is, papers with a weight average fiber length of about 85 to 100μ, are generally used.The reason for this is that ordinary pressure-sensitive copying paper prints on the surface coated with microcapsules. This is because such cases are extremely rare, and the current situation is that little consideration is given to print suitability, and this is also a good thing.

On the other hand, single pressure-sensitive recording sheets are usually used with some kind of printing applied to the recording layer (coating layer), so using sheets with the fiber lengths mentioned above will result in a rough surface. As a result, printability deteriorates, and the quality is unsatisfactory in practical terms.

Next, in the present invention, 40 parts of pulp powder with a weight average fiber length of 20 to 80 μm is added to 100 parts by weight of microcapsules.
The characteristic of using ~200 parts by weight (preferably 50 to 100 parts by weight) is closely related to the fact that the recording layer is in a single layer form.

In other words, the single-layer pressure-sensitive recording sheet F has excellent recording suitability because the microcapsules and the coloring agent are mixed and close to each other, but on the other hand, it is extremely susceptible to colored stains due to contact and rubbing. It's easy. Therefore, it was experimentally found that the above-mentioned amount must be achieved in order to obtain the No. 7 criteria for recording suitability and prevention of colored stains, and to make the product commercially valuable in terms of quality.

In this respect, compared to conventional pressure-sensitive copying paper, which uses about 20 to 30 parts of pulp powder per 100 parts by weight of microcapsules to obtain a buffing effect for copyability and prevention of color stains, it is much more effective. It can be said that the amount is completely beyond common sense for a Nutilt agent.

In this sense, the pulp fiber length and usage amount specified in the claims are essential requirements in order to make a single-layer pressure-sensitive recording sheet of commercial value in terms of quality. The bulb powder used in the present invention is one that is mechanically pulverized after acid hydrolysis, or one that is simply mechanically pulverized bulb, as long as it satisfies the condition that the weight average fiber length is 20 to 80μ. It's okay to use it, and it doesn't matter what type it is.

Further, as the coloring agent constituting the single-layer pressure-sensitive recording sheet of the present invention, for example, inorganic coloring agents such as acid clay, activated clay, bentonite, attapulgite, and silica gel, polyvalent metal salts of aromatic carboxylic acids, etc. , organic coloring agents such as phenol polymers are used as appropriate, and of course, latexes, starches, adhesives such as polyvinyl alcohol, pigments, dyes, and various other materials that are mixed into the coloring agent are used as appropriate. Auxiliary agents and the like are also used as appropriate and necessary.

Various known methods used in the production of pressure-sensitive recording sheets, such as complex coacervation method, simple coacervation method, 1n-8ituJt method, and interface type method, can be used as methods for producing color former-containing microcapsules.
The method may be used as appropriate.

Coacervation methods include two-component systems such as gelatin and gum arabic, gelatin and carboxymethylcellulose, three-component systems such as gelatin, carboxymethylcellulose, and methyl vinyl ether maleic anhydride copolymer, and microencapsulation using PVA with a clouding point. Simple coacervation methods such as 1&firaru・1n-sis
The u polymerization method includes urea-formalin resin, melamine-
Examples include formalin resin. Interfacial polymerization methods include acid chlorophyte and amine, isocyanate and water, isocyanate and polyamine, isocyanate and polyol, isothiocyanate and water, isothiocyanate and polyamide 7
, isothiocyanates and polyols.

Examples of polyvalent isocyanate compounds include aromatic polyvalent isocyanates such as phenyl dimethylene triisocyanate, tetraphenyl trimethylene tetraisocyanate, pentaphenyltetramethylene pentaisocyanate, rimethylene diisocyanate, hexamethylene diisocyanate, and fluoropylene diisocyanate. 1,2-diisocyanate, butylene-1,2-diisocyanate, ethyridine diisocyanate, or these and polyhydric hydroxy compounds, polyvalent amines, polyvalent carboxylic acids, polyvalent thiols,
Polyisocyanate prepolymers of adducts with epoxy compounds, or trimeric substances of aliphatic polyvalent isocyanates such as ethylene diisocyanate, decamethylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, and hexamethylene diisocyanate, with the structural formula (R is an aliphatic compound having one or more isocyanate groups) There are aliphatic polyvalent isocyanes F such as 4-isocyanatemethyl-1,8-octamethylene diisocyanate.

Any polydivalent amine can be used as long as it has two or more NH or N2 groups in its molecule and can be dissolved or dispersed in the hydrophilic liquid forming the continuous phase. Specific substances include diethylenetriamine, FriethyV
Aliphatic polyvalent amines such as tetramine, 1,8-propylene diamine, hexamethylene diamine, etc. Epoxy compound adducts of dialiphatic polyvalent amines: Alicyclic polyvalent amines such as hihetsucin, 3,9-bis- aminopropyl-2,
4,8,10-tetraoxanupyro(5,5')-1
Examples include heterocyclic diamines such as indecane.

Further, as the support, for example, paper, synthetic paper, synthetic film, etc. are preferably used, and the coating method is not particularly limited.

The present invention will be described in more detail with reference to Examples below, but of course the present invention is not limited thereto. Parts and % in the examples indicate parts by weight and % by weight, respectively.

Example-1 1) Preparation of microcapsule dispersion containing color former
Polymethylene polyphenylisocyanate (aromatic polyvalent isocyanate) is dissolved in this oily liquid.
Manufactured by Nippon Horiurethane Co., Ltd., product name “Millionate MR50”
Hexamethylene diisocyanate 8 having a biuret F bond which is an aliphatic polyvalent isocyanate and 4 parts of
Polyvinylbenzene-nulphonic acid (manufactured by Kanebo NSC, trade name: VE R8A-TL 5
00J) was emulsified in 200 parts of a 4% aqueous solution using a homomixer to obtain a dispersion having an average particle size of 9 μm. To this dispersion, 1.0 parts of diethylenetriamine, which is a polyvalent amine, and 0.2 parts of hexamethylene diamine were added, and after stirring at room temperature for 15 minutes, the temperature of the thread was raised to 80°C and reacted for 4 hours. The mixture was further cooled to room temperature to obtain a color former-containing microcapsule dispersion.

2) Preparation of coloring agent dispersion Sufficiently disperse 100 parts of activated clay and 4 parts of sodium hydroxide in 400 parts of water, add 20 parts of styrene-butadiene copolymer latex (solid content 50%), A coloring agent dispersion was obtained.

8) Production of single-layer pressure-sensitive recording sheet t 50 parts of the above color former-containing microcapsule dispersion (in terms of solid content), 100 parts of color former dispersion (in terms of solid content), weight average fiber length 50 parts of pulp powder having a diameter of 56 microns were mixed to obtain a uniform single coating solution. This single coating liquid had good fluidity even at a concentration of 35%, and there were no problems with the liquid properties of the coating liquid. This single coating liquid was coated onto a support by air knife coating so that the coating amount was 10 f to obtain a single pressure-sensitive recording sheet in the form of a single layer.

Example-2 1) Preparation of microcapsule dispersion containing color former 100 parts of 3% ethylene/maleic anhydride copolymer aqueous solution, 1 part of urea
0 parts and 1 part of resorcin were dissolved in 200 parts of water, and the pH was adjusted to 3.3 using a 20% aqueous sodium hydroxide solution. One part of Crystal Violet Tsuk was dissolved in 100 parts of diisopropylnaphthalene and emulsified in the above mixed aqueous solution using a homomixer to obtain a dispersion having an average particle size of 4.6 μm. 3
25 parts of a 7% formaldehyde aqueous solution was added, and the thread was heated to 55° C. while stirring, and after 2 hours was allowed to cool to obtain a capsule dispersion.

2) Preparation of color former dispersion 60 parts of a styrene polymer with a melting point of 121°C is heated and melted at 180°C, and 10 parts of zinc salt of 3,5-di(α-methylbenzyl)salicylic acid is dissolved and mixed therein. did. After cooling and solidifying, the coloring agent particles obtained by coarsely crushing the particles were mixed with sodium butylnaphthalene sulfonate (trade name: Perex NBL).
, manufactured by Kao Atranu Co., Ltd.) and 25 parts of a 10% aqueous solution of polyvinyl alcohol (trade name PTA-117, manufactured by Kuraray Co., Ltd.) was added to 500 parts of water, and the resulting dispersion was mixed with a continuous sand grinder. Fine sea bream processed. The average particle size of the coloring agent fine particles was 3.4μ.

To this dispersion were further added 40 parts of finely powdered zinc silicate, 100 parts of kaolin, 200 parts of 1O% oxidized starch aqueous solution and 200 parts of water, and after thorough stirring, styrene-butadiene copolymer latex (solid content 50 parts) was added. %) was added and mixed with stirring to obtain a coloring agent dispersion.

8) Production of a single pressure-sensitive recording sheet in the form of a single layer: 100 parts of the above color former-containing microcapsule dispersion (calculated as solid content);
100 parts of a coloring agent dispersion (in terms of solid content) and 80 parts of pulp powder having a weight average fiber length of 72 microns were mixed to obtain a uniform single coating solution. This single coating liquid had good fluidity even at a concentration of 35%, and there were no problems with the liquid properties of the coating liquid. This single coating liquid was used in the same manner as in Example 1 to obtain a single pressure-sensitive recording sheet in the form of a single layer.

Example 3 1) Preparation of color former-containing microcapsule dispersion 3 parts of crystal violet lactone was dissolved in 100 parts of diisopropylnaphthalene, and this was emulsified and dispersed in 400 parts of a 5% aqueous solution of acid-treated zeftin at 55°C. Furthermore, 400 parts of a 5% aqueous gum arabic solution was added, and while maintaining the liquid temperature at 55°C, a 5% acetic acid aqueous solution was added dropwise to adjust the pH of the thread to 4.0, and while stirring was continued, the liquid temperature was lowered to 10°C. Next, 20 parts of a 10% formalin aqueous solution was added to the flask, followed by a 10% sodium hydroxide aqueous solution to adjust the pH of the thread to 10.0, followed by stirring for 10 hours to obtain a capsule dispersion.

2) Preparation of coloring agent dispersion A color former dispersion liquid was obtained in the same manner as in Example-2.

100 parts of the above color former-containing microcapsule dispersion (in terms of solid content), 150 parts of the color former dispersion (in terms of solid content), and 100 parts of pulp powder with a weight average fiber length of 35 microns are mixed to form a uniform single product. A coating liquid was obtained.

This single coating liquid had good fluidity even at a concentration of 35%, and there were no problems with the liquid properties of the coating liquid. Example of this single coating liquid
A single pressure-sensitive recording sheet F in the form of a single layer was obtained in the same manner as in Example 1.

Example 4 1) Preparation of microcapsule dispersion containing a color former 77173 parts of crystal violet was dissolved in 100 parts of diisopropylnaphthalene, and polymethylene polyphenylisocyanate (manufactured by Nippon Polyurethane Co., Ltd.), which is an aromatic polyvalent isocyanate, was dissolved in this oily liquid. , Product name: “Millione) MR
500 J) and 10 parts of a trimer of hexamethylene diisocyanate having an isocyanurate-F ring as an aliphatic polyvalent isocyanate are dissolved.

Polyvinyl alcohol (manufactured by Kuraray Co., Ltd., product name “PVA-”)
1174') was emulsified in 800 parts of a 5% aqueous solution using a homomixer to obtain a dispersion having an average particle size of 11 μm. Two parts of a polyvalent amine adduct of bisphenol A, epichlorohydrin, and alkylamine were added to this dispersion, and 1 part of the mixture was heated at room temperature.
After stirring for 5 minutes, the temperature of the system was raised to 90° C., the reaction was allowed to proceed for 4 hours, and the mixture was further cooled to room temperature to obtain a color former-containing microcapsule dispersion.

2) Preparation of color former dispersion A color former dispersion was obtained in the same manner as in Example-1. 3) Production of a single layer pressure-sensitive recording sheet The above color former containing microcapsule dispersion 100 yen (solid content equivalent),
A uniform single coating liquid was obtained by mixing 200 parts of a coloring agent dispersion (in terms of solid content) and 100 parts of pulp powder with a weight average fiber length of 49 microns. This single coating liquid had fluidity even at a concentration of 35%. There were no problems with the liquid properties of the coating liquid. Example of this single coating liquid
Comparative Example-1 A single-layer pressure-sensitive recording sheet was obtained in the same manner as in Example 1. A single-layer pressure-sensitive recording sheet was obtained in the same manner as in Example-1 except that the pulp powder of Example-1 was not added. A record sheet t was obtained.

Comparative Example 2 A single pressure recording sheet in the form of a single layer was obtained in the same manner as in Example 2 except that the bulb powder in Example 2 was replaced with starch granules.

Comparative Example 8 A single-layer pressure-sensitive recording sheet was obtained in the same manner as in Example 8, except that the valve powder of Example 8 was replaced with pulp powder having a weight average fiber length of 85 microns.

Comparative Example 4 A single-layer pressure-sensitive recording sheet was obtained in the same manner as in Example 4, except that the pulp powder in Example 4 was changed to a pulp powder with a weight average fiber length of 92 microns.

Quality tests were conducted on the single pressure-sensitive recording sheets of the eight types of single-layer dust thus obtained, and the results are listed in Table 1.

Table 1 (Note) Recording densities are recorded using a typewriter (I (ermes-70).
0EL), then press color under the following conditions. - Type: 2W11 square solid type - Type pressure: + (strong) 8 hours after color development, measure the color density using a Macbeth color densitometer (Red Filter). (The larger the value, the better the recording suitability) Press stains were measured using a Macbeth densitometer (Red Filter) as colored stains generated when pressing at 60 kq/ant.

(The larger the number, the worse the press stains are.) To check for abrasion stains, place the high-quality paper and single pressure-sensitive recording sheet so that their coated surfaces face each other, and apply a load of 800 f/Ca. The recording surface was rubbed several times, and colored stains on the recording surface were visually judged.

(A: little stain, B: much stain) Ink receptivity was determined by printing the coated surface of a single pressure-sensitive recording sheet with an R1 printing machine (R1 tester manufactured by Mei Seisakusho). The receptivity of the ink to the surface of the pressure recording sheet was visually judged.

Patent applicant: Kanzaki Paper Co., Ltd.

Claims (1)

[Claims] In a single pressure-sensitive recording sheet made by coating a support with a uniform mixture of color-forming agent-containing microcapsules and a color-forming agent and drying it,
The homogeneous mixed liquid is characterized by containing 40 to 200 parts by weight of pulp powder having a weight average fiber surface (TAPPI standard T232.8U-as) of 20 μ to 80 μ per microcapsule 10 ONN solid content). Single pressure sensitive recording sheet.